Selenium and thyroid function

The thyroid system regulates and maintains many vital functions in the body. To ensure its optimal functioning, the thyroid gland requires adequate levels of selenium and iodine.

Selenium is an essential micronutrient. We need only small quantities of it, but we do need selenium as a component of the amino acid selenocysteine. We need the selenocysteine, in turn, for the body’s synthesis of 25 identified selenoproteins that have a variety of biological functions [Bellinger].

Selenium and thyroid function

The thyroid is the small butterfly-shaped gland at the base of our necks, just above our breastbones. For such a small gland, the thyroid gland is very important. When it is healthy, it produces the hormones that regulate many bodily functions:

the body’s metabolism rate

the body’s heart function

the functioning of the digestive system

the body’s muscle control

the brain’s development

the maintenance of good bone health

Diseases inhibiting thyroid gland function

The most prevalent diseases of the thyroid gland are the following [Iddah]:

Selenium supplementation may reduce the extent of the damage to cells caused by the binding of lymphocytes and/or thyroid auto-antigens to thyroid cell membranes [Schomburg].

Selenium supplementation and autoimmune thyroid diseases

A 2017 comprehensive review of the bio-medical literature on selenium and thyroid disease suggests that selenium supplementation of patients with autoimmune thyroid diseases is associated with the following beneficial health effects [Ventura]:

reductions in anti-thyroperoxidase antibody concentrations

improved thyroid ultrasound images

improved quality of life

Note: The thyroid peroxidase enzymes play an important role in the production of thyroid hormones. In autoimmune diseases, the body mistakenly produces antibodies that attack these important enzymes. Adequate selenium status seems to reduce the risk of these mistaken autoimmune attacks.

Selenium supplementation and Hashimoto’s disease

Hashimoto’s disease is an autoimmune disease in which the immune system’s T-cells mistakenly attack the thyroid gland, especially the thyroid peroxidase enzymes. Hashimoto’s disease causes the following symptoms in the thyroid gland:

chronic inflammation

damage to the thyroid tissue

reduced thyroid activity (hypothyroidism)

A 2014 Cochrane review of clinical studies involving selenium supplementation in addition to levothyroxine T4 hormone replacement therapy showed that the selenium supplementation is associated with a reduction in the concentrations of circulating auto-antibodies [van Zuuren].

At present, we are awaiting the outcome of the CATALYST randomized controlled study. The study is designed to test the hypothesis that a 12-month daily intervention with 200 micrograms of a selenium-enriched yeast will be beneficial in the treatment of chronic autoimmune thyroiditis. The primary outcome measured in the study is the thyroid-related quality of life assessed by the Thyroid Patient-Reported Outcome (ThyPRO) questionnaire [Winther].

Selenium supplementation and Graves’ disease

In cases of autoimmune hyperthyroidism caused by Graves’ disease, such symptoms as rapid heartbeat, weight loss, and mental disturbances (including anxiety and depression) are common. A 2015 study has shown that daily supplementation with 200 micrograms of selenium can improve the immune system responses, the hormone levels, and the symptoms of patients [Calissendorf].

A 2011 randomized controlled study has shown found that selenium supplementation improves the well-being of patients affected by Graves’ disease, an autoimmune thyroid disease leading to excessively high thyroid activity [ Marcocci].

The GRASS study now in progress [Watt] has been designed to test the hypothesis that selenium supplementation in addition to standard treatment will have beneficial effects on autoimmune hypothyroidism in the following ways:

decrease in anti-thyroid drug treatment failure

faster and longer lasting remission

improved quality of life for patients

Summary of selenium and autoimmune thyroid disease literature

What do we know about selenium supplementation and autoimmune thyroid disease [Winther 2017]?

1989 Professor G.G. Duthie publishes evidence for a role of selenium in the prevention of cardiovascular disease

1993 Researcher W.J. Blot publishes the results of the Nutrition Intervention Trials in Linxian, China, showing that supplementation with a combination of selenium and other antioxidants reduces the risk of cancer

1994 Professor G.N. Schrauzer publishes evidence that selenium is important in the maintenance and therapy of HIV-infected patients

2002 Researcher Margaret Rayman presents the arguments for increasing selenium intakes to realize selenium’s antioxidant and anti-viral and anti-inflammatory effects as well as selenium’s enhancement of immune function and reproductive success.